Tick fix (Important!)

MAJOR: In commit bacb8a7, the `Ticker._lastTime = time` update was changed to `Ticker._lastTime = adjTime`, which is wrong - this results in wrong value on elapsedTime (thus, on event.delta).

MINOR(s): getMeasuredTickTime and getMeasuredFPS now verifies if times list is null, so if we call them before Ticker initialization, they don`t throw errors.